Regardless of the quantity of leads tied together in the box, if the switch itself only has two wires or screws on it where connections are made, you can replace it with a standard on/off wall switch. Tieing all of the white (neutral) leads together is fairly common as you switch the hot lead (normally black or red for switched). tying blacks together just means it is feeding multiple places. All a 'normal' switch does is connect two leads together, and break the connection when off. So, if there are only two leads, connect them one to each screw of a new switch, doesn't matter which one goes where.